President Bush will create three new marine national monuments in the Pacific Ocean today, according to his top aides, a move that will help preserve sprawling sea and island ecosystems and cement the one aspect of his legacy that has won praise, sometimes grudgingly, from many environmentalists.

Bush's decision to safeguard far-flung areas totaling 195,280 square miles, which comes just two weeks before he leaves office, underscores his contradictory environmental record. While he has resisted imposing mandatory curbs on greenhouse gas emissions linked to climate change and has opened large areas of the nation to drilling, mining and other use of resources, by the end of his term he will have protected more ocean than any person in history.

Invoking powers of the Antiquities Act of 1906 that are used to protect statues and cultural sites, Bush will sharply restrict oil and gas exploration and commercial fishing around numerous remote islands in the central and western Pacific that have long been U.S. possessions. Scientists identified them as biologically and geologically rich areas. The monuments, which together are equal in size to Spain, include regions teeming with sharks and other top marine predators, along with vibrant coral and hydrothermal vents.

James L. Connaughton, who chairs the White House Council on Environmental Quality, said the new designations, coupled with Bush's 2006 decision to create the Papahanaumokuakea Marine National Monument in the Northwestern Hawaiian Islands and a handful of smaller designations, mean that Bush has matched the record of some of the nation's most conservation-minded presidents. Spanning an additional 138,000 square miles, the Hawaiian monument is one of the world's largest protected marine reserves.

"In the last eight years, we've been able to accomplish conservation in marine environments on par with what we've achieved on land over the past 100 years," Connaughton said in an interview.

In making the decision, Bush overruled the objections of recreational fishing interests and Vice President Cheney, who argued that the restrictions would create a dangerous precedent. Recreational fishermen will be required to apply for permits to fish in the protected areas.

Bush, a fisherman himself, has consistently demonstrated more of an interest in marine issues than in other environmental matters, even making ocean conservation the theme of last year's Easter Egg Roll. First lady Laura Bush, an avid bird-watcher, weighed in as well, soliciting input from outside scientists, asking for briefings on the proposed monument designations, and privately telling some participants in the process that she considers the monuments a key part of her husband's environmental legacy.

Among the unique ecological treasures that will receive new protection are the giant coconut crab, the largest land-living arthropod; an endangered bird that incubates its eggs with volcanic heat; a boiling pool of liquid sulfur; and a 31-mile-wide active mud volcano.

Joshua S. Reichert, managing director of the Pew Environment Group, said Bush "has ushered in a new era of ocean conservation in the United States and the world at large" with his push to protect ecologically valuable marine areas.

"It has taken 137 years, since the creation of America's first national park in Yellowstone in 1872, to recognize that unique areas of the world's oceans deserve the same kind of protection as we have afforded similar places on land," Reichert said. "And none too soon."

But Vikki Spruill, president and chief executive of the Ocean Conservancy, an advocacy group, cautioned that in light of Bush's other policies, it is too early to judge the impact of the new protections.

"On balance, when you compare this to little to no action on climate change and the lifting of the moratorium [on offshore oil drilling] that's been in place for 27 years, that begins to paint a different picture," she said. "This move, by itself, is a really positive move. The net gain is a question we will have to address years from now."